Spring-less control valve for a percussion machine driven by pressure fluid

ABSTRACT

In a device which is actuated by means of pressurized fluid, a spring-less control valve for the fluid under pressure which is in turn controlled by an auxiliary valve. The control valve has a reciprocable valve body formed as a differential piston. A reciprocable slidable blocking piston is disposed adjacent to the valve body and is adapted to assume a first blocking position in which the opening movement of the valve body is blocked and the fluid under pressure is not acting on said blocking piston and a second open position in which the path of movement of the valve body is unblocked and in which the fluid under pressure acts on the valve body.

United States Patent 1191 1111 3,871,405 Schwarz Mar, 18, 1975 [5 SPRING-LESS CONTROL VALVE FOR A 3,170,487 2/1965 Juilfs l37/625.6

3,181,566 5/l965 Volkmann l37/625.6

PERCUSSION MACHINE DRIVEN BY PRESSURE FLUID Primary Examiner-Alan Cohan [75] Inventor: Heinz Schwarz, Ziz ishausen,

Germany 57 ABSTRACT Assigneei Karl Reich Maschinenfabi'ik In a device which is actuated by means of pressurized Nuertmgeni Germany fluid, a spring-less control valve for the fluid under 22 Filed; u 22 1973 pressure which is in turn controlled by an auxiliary valve. The controlvalve has a reciprocable valve body [2] 1 Appl- N03 390,617 formed as a differential piston. A reciprocable slidable blocking piston is disposed adjacent to the valve body 52 us. c1 l37/624.27, 137/6256, 91/461 and is adapted to assume a first blocking Position in 511 1m. 01. FlSb 31/01 Which the Opening movement of the valve body is [5 Field of Search n 91/461 blOCkfiCl and the fluid under pressure iS I'lOlI acting on said blocking piston and a second open position in he valve body is un- [56] References c which the path of movement of t blocked and in which the fluld under pressure acts on UNITED STATES PATENTS the Valve body. 2,859,735 ll/l958 Di Tirro l37/624.27 X

3,011,519 12/1961 Brinkel l37/624.27 6 Clalms, 3 Drawing Flgures y Y fiiti/ /a 49/ i T 4 -24 Z 2/? 3 9 I 34 Ill PATENTED MR 1 8 I975 SHEEI 1 [If 2 BACKGROUND OF THE INVENTION The present invention relates to a spring-less control valve for fluid under pressure which is controlled by means of an auxiliary valve. The spring-less control valve has a valve body which is formed as a differential piston. Such control valves are generally used in pneumatic percussion machines for driving nails, staples or the like in which the aforementioned fastening means are driven into the work piece by means of a pneumatically actuated percussion piston. In order to attain the necessary high percussion energy there must be provided control valves with large cross-sectional diameter, which can be suddenly opened. In order to accomplish this, the valve body of the control valve is generally formed as a differential piston, that is it is controlled by means of an auxiliary valve with air under pressure. The auxiliary valve is easily manually actuated by a person servicing the device.

The valve body for the control valve is acted on by pressurized air in such a way that it is maintained in a closed position. In order to support this holding force, a suitable spring can be provided. When the control valve is to be opened, the pressurized air is then guided so that it moves the valve body into its opened position, so that the pressurized air can flow into the cylinder in which the percussion piston is disposed.

Thus, in the embodiment where the valve body is formed as a differential piston without springs this valve body is exclusively maintained in its inoperative position by means of pressurized air. This, of course, means that when the percussion machine is disconnected from its pressurized air supply, the aforementioned holding force disappears and the valve body remains in its closed position exclusively by the action of frictional forces. If the percussion machine is unintentionally subjected to blows while being transported, it is then possible that the valve body is slid into its open position. When thereafter the percussion machine is again connected to a source of pressurized air, then the pressurized air can flow into the percussion cylinder before the pressurized air has slid the valve body due to its differential working surfaces into its closed position. There thus then results an undesirable actuation of the percussion piston, independent from the actuation of the auxiliary valve by a person servicing the device.

This undesirable actuation can be avoided by means of a spring, which prevents an undesirable sliding of the valve body into its open position during the time interval the percussion machine is not in a pressurized condition. However, such a spring is subjected during the operation of the device to very large forces which quickly wear it out, in particular in view of the percussion type of operation of the device, which only very strong springs can withstand for long periods of time. In addition thereto, a spring of the aforedescribed type negatively influences the overall constructional arrangement of the control valve.

SUMMARY OF THE INVENTION It is a principal object of the invention to provide a locking mechanism for a control valve for percussion machines which are driven with pressurized fluid,

wherein a sliding of the valve body during a nonpressurized condition of the machine is avoided without requiring a spring for coaction with the valve body.

This object of the invention is obtained by providing a blocking mechanism which is slidable by means of the pressurized fluid and which is mounted adjacent to the valve body, so that in a first position, wherein the pressurized medium does not energize the percussion machine, the opening movement of the valve body is blocked, and in a second position, wherein the pressurized medium acts on the percussion piston of the machine, the operational path of the valve body of the control valve is unblocked. Due to this arrangement the percussion machine is secured against the release of an undesirable blow by the percussion means when the percussion machine is connected to a source of pressurized fluid, said blow being carried out due to the inadvertant opening of the control valve which causes the entry of pressurized fluid into the percussion cylinder.

The blocking or locking means of the invention are advantageously formed as a blocking piston having a blocking pin, both of which are arranged perpendicularly to the axis of the valve body. This blocking piston is maintained in its blocking position by means of a spring. When the percussion machine is connected to a source of pressurized fluid, i.e., pressurized air, the blocking piston is slidably moved, against the action of its spring, and thereby the blocking pin is moved out of the operational path of the valve body. In order'to assure that the inflowing pressurized fluid slides the valve body into its closing position, before the blocking piston of the blocking means is moved outwardly, the pressurized fluid acts on the blocking piston via a throttling bore. There thus results a delayed sliding of the blocking piston into the blocking position relative to the movement of the valve body.

The blocking piston may advantageously be movably mounted in a screwed socket which is screwed into the housing of the percussion machine. This embodiment renders the advantage that the blocking piston is easily accessible and the blocking means can be easily exchanged, and furthermore, the surface of the cylindrical bore in which the blocking piston is mounted can be easily serviced.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated by way of example in connection with the accompanying drawings, which form part of this application and in which:

FIG. 1 is a side view of a pneumatic percussion machine in accordance with this invention, which is partially shown in section for sake of clarity;

FIG. 2 is a cross-sectional view through the control valve of a pneumatic percussion machine including the blocking means, wherein the percussion machine is not fed with pressurized air;

FIG. 3 is an enlarged view of a portion of FIG. 2 shown in cross-section, wherein the pneumatic percussion machine is fed with pressurized air.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now to the drawings there is illustrated a housing I wherein there is mounted a percussion cylinder 2 in which a percussion piston 3 is movably mounted. A handle 4 is firmly secured to the housing 1. The handle 4 has a hollow inner space 5 (FIG. 1).

a sliding movement of the valve body 7 into its open position. f t

It is to be understood that the blocking arrangement in accordance with this invention cannot only be used in conjunction with control valves for pneumatic nailing machines, but all other types of pressurized fluid actuated percussion machines, wherein the control valve includes a valve body which is formed as a spring-less differential piston, whereby any pressurized fluids, gaseous or liquid, can be used.

Although the invention is illustrated and described with reference to one preferred embodiment thereof, it is to be expressly understood that it is in no way limited to the disclosure of such a preferred embodiment, but is capable of numerous modifications within the scope of the appended claims.

What is claimed is:

1. In a pneumatic nailing machine which is actuated by pressurized air from a source of compressed air, an improved spring-less control valve for controlling the fiow of the pressurized air, said control valve having a valve body formed as a differential piston and having opposite reactor surface areas which is reciprocably slidably mounted in said machine to move between an open and closed position, and arranged to be urged closed by pressure applied to both reactor surface areas, means communicating at least one of the reactor surface areas directly with said source of compressed air, a blocking piston reciprocably slidable in said machine adjacent to said valve body so as to move between a first blocking position and a second retracted position relative to said valve body, said blocking piston moving into said first blocking position when not acted on by said pressurized air and into said second retracted position when acted on by said pressurized air, means for venting the larger reactor surface to cfthe blocking piston, the improvement comprising conduit means which directly communicate said source of compressed air with said blocking piston.

2. In the pneumatic nailing machine, the spring-less control valve as set forth in claim 1, including a cylindrical recess in said machine in which said blocking piston is slidably mounted, a spring operatively connected to said blocking piston, said compressed air acting on said blocking piston in opposition to said spring.

3. In the pneumatic nailing machine, the spring-less control valve as set forth in claim 2, including cylindrical wall means defining said cylindrical recess, a conduit for conducting compressed air from said source to said valve body, a throttling bore extending through said cylindrical wall means to said conduit.

4. In the spring-less control valve as set forth in claim 3, wherein said blocking piston comprises a blocking pin which coaxially extends therefrom into the path of movement of said valve body when said blocking piston is in its blocking position.

5. In the pneumatic nailing machine, the spring-less control valve as set forth in claim 4, wherein said valve body is formed as an annular differential piston having a pair of opposite end faces, the axis of said annular differential piston being perpendicular to the axis of said cylindrical recess and said blocking piston, said block ing pin being adapted to be contacted by one of said end faces of said differential piston when said blocking piston is in its blocking position.

6. In the pneumatic nailing machine, the spring'less control valve as set forth in claim 5, including a socket threadably mounted in said device having formed therein said cylindrical recess. 

1. In a pneumatic nailing machine which is actuated by pressurized air from a source of compressed air, an improved spring-less control valve for controlling the flow of the pressurized air, said control valve having a valve body formed as a differential piston and having opposite reactor surface areas which is reciprocably slidably mounted in said machine to move between an open and closed position, and arranged to be urged closed by pressure applied to both reactor surface areas, means communicating at least one of the reactor surface areas directly with said source of compressEd air, a blocking piston reciprocably slidable in said machine adjacent to said valve body so as to move between a first blocking position and a second retracted position relative to said valve body, said blocking piston moving into said first blocking position when not acted on by said pressurized air and into said second retracted position when acted on by said pressurized air, means for venting the larger reactor surface to effect opening of the control valve when not blocked by the blocking piston, the improvement comprising conduit means which directly communicate said source of compressed air with said blocking piston.
 2. In the pneumatic nailing machine, the spring-less control valve as set forth in claim 1, including a cylindrical recess in said machine in which said blocking piston is slidably mounted, a spring operatively connected to said blocking piston, said compressed air acting on said blocking piston in opposition to said spring.
 3. In the pneumatic nailing machine, the spring-less control valve as set forth in claim 2, including cylindrical wall means defining said cylindrical recess, a conduit for conducting compressed air from said source to said valve body, a throttling bore extending through said cylindrical wall means to said conduit.
 4. In the spring-less control valve as set forth in claim 3, wherein said blocking piston comprises a blocking pin which coaxially extends therefrom into the path of movement of said valve body when said blocking piston is in its blocking position.
 5. In the pneumatic nailing machine, the spring-less control valve as set forth in claim 4, wherein said valve body is formed as an annular differential piston having a pair of opposite end faces, the axis of said annular differential piston being perpendicular to the axis of said cylindrical recess and said blocking piston, said blocking pin being adapted to be contacted by one of said end faces of said differential piston when said blocking piston is in its blocking position.
 6. In the pneumatic nailing machine, the spring-less control valve as set forth in claim 5, including a socket threadably mounted in said device having formed therein said cylindrical recess. 